public static double[] FirFilter(double[] data, double hz, int n, double threshold0, double threshold1, FirFilterType type = FirFilterType.LowPass, FirWindowType windowType = FirWindowType.Rectangle)
{
double[] h = ImpulseCharacteristic(hz, n, threshold0, threshold1, type, windowType);
return(BaseFirFilter(data, h));
}
public static double[] ImpulseCharacteristic(double hz, int n, double threshold, FirFilterType impulseCharacteristicType = FirFilterType.LowPass, FirWindowType windowType = FirWindowType.Rectangle)
{
double[] h;
double[] w = WindowCoef(windowType, n);
double fc = threshold / (hz);
switch (impulseCharacteristicType)
{
case FirFilterType.LowPass:
h = BaseImpulseCharacteristic(threshold, hz, n);
break;
case FirFilterType.HighPass:
h = BaseImpulseCharacteristic(threshold, hz, n).Select(x => (-x)).ToArray();
h[n / 2] = 1 - 2 * fc;
break;
default:
throw new Exception();
}
double[] result = new double[n];
for (int i = 0; i < n; i++)
{
result[i] = h[i] * w[i];
}
return(result);
}
public static double[] ImpulseCharacteristic(double hz, int n, double threshold0, double threshold1, FirFilterType impulseCharacteristicType = FirFilterType.LowPass, FirWindowType windowType = FirWindowType.Rectangle)
{
double[] h0, h1, h;
double[] w = WindowCoef(windowType, n);
double fc0 = threshold0 / (hz);
double fc1 = threshold1 / (hz);
switch (impulseCharacteristicType)
{
case FirFilterType.BandPass:
h = new double[n];
h0 = BaseImpulseCharacteristic(threshold0, hz, n);
h1 = BaseImpulseCharacteristic(threshold1, hz, n);
for (int i = 0; i < n; i++)
{
h[i] = h1[i] - h0[i];
h[n / 2] = 2 * (fc1 - fc0);
}
break;
case FirFilterType.NotchPass:
h = new double[n];
h0 = BaseImpulseCharacteristic(threshold0, hz, n);
h1 = BaseImpulseCharacteristic(threshold1, hz, n);
for (int i = 0; i < n; i++)
{
h[i] = h0[i] - h1[i];
h[n / 2] = 1 - 2 * (fc1 - fc0);
}
break;
default:
throw new Exception();
}
double[] result = new double[n];
for (int i = 0; i < n; i++)
{
result[i] = h[i] * w[i];
}
return(result);
}
